100-125mm TL for Mitutoyo to cover FF sensor?

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Medwar
Posts: 72
Joined: Mon Apr 16, 2012 1:46 am

100-125mm TL for Mitutoyo to cover FF sensor?

Post by Medwar »

Hi all!

I think many here had a lot of experimenting with different tube lenses (TL) for focusing Mitutoyo infinity objectives.
Is there any tube lens that will allow the Mitutoyos (5x 0.14, 10x 0.28, 20x 0.42) to
1) work at 0,5 - 0,625 of their nominal magnification (it means TL in range 100mm-125mm)
2) cover the 35mm full frame sensor without resolution loss, except, maybe, extreme corners and showing more or less uniform resolution all over a modern 45-60 Mpix FF sensor

Does anyone have a successful impementation of such setup?

I have read somewhere that Raynox DCR-250 and DCR-150 do cover FF, but when used for nominal magnifications e.g. 5x for 5x 0.14.
But how does 125mm DCR-250 perform on a high-res FF sensor for 5x 0.14 objective pushed down to 3x?

lothman
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Location: Stuttgart/Germany

Re: 100-125mm TL for Mitutoyo to cover FF sensor?

Post by lothman »

Medwar wrote:
Wed Jul 14, 2021 8:32 am
Hi all!

I think many here had a lot of experimenting with different tube lenses (TL) for focusing Mitutoyo infinity objectives.
Is there any tube lens that will allow the Mitutoyos (5x 0.14, 10x 0.28, 20x 0.42) to
1) work at 0,5 - 0,625 of their nominal magnification (it means TL in range 100mm-125mm)
2) cover the 35mm full frame sensor without resolution loss, except, maybe, extreme corners and showing more or less uniform resolution all over a modern 45-60 Mpix FF sensor

Does anyone have a successful impementation of such setup?

I have read somewhere that Raynox DCR-250 and DCR-150 do cover FF, but when used for nominal magnifications e.g. 5x for 5x 0.14.
But how does 125mm DCR-250 perform on a high-res FF sensor for 5x 0.14 objective pushed down to 3x?
I don`t think this could be possible. You can shrink the full frame image circle of the Mitus by a shorter tube lens down to APS-C and therefore decrease the magnification. But if this trick should work at full frame, this would require a much bigger image circle than the Mitus have. So you will get severe vignetting or strong degradation towards the corners.

Scarodactyl
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Re: 100-125mm TL for Mitutoyo to cover FF sensor?

Post by Scarodactyl »

I know there was some success using them on medium format, though even in the best case the corners were not very good.

Lou Jost
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Re: 100-125mm TL for Mitutoyo to cover FF sensor?

Post by Lou Jost »

I have read somewhere that Raynox DCR-250 and DCR-150 do cover FF, but when used for nominal magnifications e.g. 5x for 5x 0.14.
There looks to be some confusion here. You only get nominal magnification if you use a tube lens of the nominal focal length. So the DCR 250 can never give you nominal magnification. It will push down the objective's m, though not quite as much as you want.
I know there was some success using them on medium format, though even in the best case the corners were not very good.
Nathanm published some nice posts on that. He found that the 20x had a particularly large good image circle. The 7.5x is also known to have an especially large good image circle relative to the other Mitutoyos. Those would be the best objectives for you to work with.

Beatsy has published some tube lens tests here showing that some short Pentax telephotos are unusually good tube lenses for pushing down objectives. I do not remember the exact post. But I have been using some Pentax tube lenses and they do indeed work well for pushing down.

I did some pushng-down tests on APS some time ago and published them here, but I have not done it on FF. I would like to do some similar tests on FF.

Robert O'Toole has published extensively on this subject; you should search this forum for his posts and look at his website:
www.closeuphotography.com

Medwar
Posts: 72
Joined: Mon Apr 16, 2012 1:46 am

Re: 100-125mm TL for Mitutoyo to cover FF sensor?

Post by Medwar »

lothman wrote:
Wed Jul 14, 2021 1:59 pm
I don`t think this could be possible. You can shrink the full frame image circle of the Mitus by a shorter tube lens down to APS-C and therefore decrease the magnification. But if this trick should work at full frame, this would require a much bigger image circle than the Mitus have. So you will get severe vignetting or strong degradation towards the corners.
Thank you!
But at first glance that goes contrary with Nathan's findings about medium format:
viewtopic.php?f=25&t=32346

Please correct me if I am wrong:

MF = 60mm, FF=35mm, ratio = 35/60 = 0.58
Being able to cover MF on nominal M (magnification) should mean ability to cover FF on 0.58*M
(if we make a supposal that the image is not degraded from pushing the objective down)
0.58 is even less than 0.625 (ratio of Mitu mag with a 125mm TL), so we should have even a little less side and corner problems on FF with 125mm TL than on MF with ~200mm TL.

The only argument why it DID cover MF on nominal M but theoretically can't cover FF on 0.625*M, that I can invent here, is that Nathan tested MF on an older generation sensor with large pixels, while the same setup could possibly be worse in resolution on modern sensor with tiny pixels.
Last edited by Medwar on Thu Jul 15, 2021 2:00 am, edited 3 times in total.

Medwar
Posts: 72
Joined: Mon Apr 16, 2012 1:46 am

Re: 100-125mm TL for Mitutoyo to cover FF sensor?

Post by Medwar »

Lou Jost wrote:
Wed Jul 14, 2021 8:55 pm
There looks to be some confusion here. You only get nominal magnification if you use a tube lens of the nominal focal length. So the DCR 250 can never give you nominal magnification. It will push down the objective's m, though not quite as much as you want.
Thank you for pointing this out, you are right, 125mm DCR-250 will give 0.625*M, not nominal.

Medwar
Posts: 72
Joined: Mon Apr 16, 2012 1:46 am

Re: 100-125mm TL for Mitutoyo to cover FF sensor?

Post by Medwar »

Lou Jost wrote:
Wed Jul 14, 2021 8:55 pm
I know there was some success using them on medium format, though even in the best case the corners were not very good.
Nathanm published some nice posts on that. He found that the 20x had a particularly large good image circle. The 7.5x is also known to have an especially large good image circle relative to the other Mitutoyos. Those would be the best objectives for you to work with.

Beatsy has published some tube lens tests here showing that some short Pentax telephotos are unusually good tube lenses for pushing down objectives. I do not remember the exact post. But I have been using some Pentax tube lenses and they do indeed work well for pushing down.

I did some pushng-down tests on APS some time ago and published them here, but I have not done it on FF. I would like to do some similar tests on FF.

Robert O'Toole has published extensively on this subject; you should search this forum for his posts and look at his website:
www.closeuphotography.com
Thank you!
I have scrutinized Robert o'Toole's site fully before. Absolutely incredible level of testing!
But if I am not mistaken, all 100mm-150mm tube lens tests there are for APS-C (Sony a6300), not FF. So the tests doesn't provide info on whether 135mm and 150mm TLs tested cover FF or not.

I have also seen Nathanm's topic before. I wrote about it in my answer to lothman here.

I have never seen posts on Pentax lenses by Beasty. Thank you for pointing on them! I have to do some search.
Is it about old Pentax primes? I wonder if they are as good enough in resolution and aberration management as raynox or ITL200 or Schneider.
So far all old primes (e.g. Takumars) that I have tested (on APS-C) gave worse resolution and CA than raynox.

chris_ma
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Location: Germany

Re: 100-125mm TL for Mitutoyo to cover FF sensor?

Post by chris_ma »

Medwar wrote:
Thu Jul 15, 2021 1:44 am
Please correct me if I am wrong:

MF = 60mm, FF=35mm, ratio = 35/60 = 0.58
Not totally sure if you mean image circle by these numbers, but if so your calculations are indeed off. It depends which „medium format“, but I seem to remember that Nathan uses a fuji gfx, that would be an image circle off 55mm, and FF is 42mm, so the ratio would result in 0.76
chris

Medwar
Posts: 72
Joined: Mon Apr 16, 2012 1:46 am

Re: 100-125mm TL for Mitutoyo to cover FF sensor?

Post by Medwar »

chris_ma wrote:
Thu Jul 15, 2021 2:54 am
Medwar wrote:
Thu Jul 15, 2021 1:44 am
Please correct me if I am wrong:

MF = 60mm, FF=35mm, ratio = 35/60 = 0.58
Not totally sure if you mean image circle by these numbers, but if so your calculations are indeed off. It depends which „medium format“, but I seem to remember that Nathan uses a fuji gfx, that would be an image circle off 55mm, and FF is 42mm, so the ratio would result in 0.76
Right, I should have taken the diagonal size.
Then it seems logical, that Mitus cannot cover FF with 125mm TL.

pawelfoto
Posts: 90
Joined: Tue Mar 09, 2021 2:51 pm
Location: Poland

Re: 100-125mm TL for Mitutoyo to cover FF sensor?

Post by pawelfoto »

I'm not an expert. I use Canon 5d Mark IV + Mitutoyo infinity objectives + Raynox DCR150 on 200mm tube and DCR250 on 125mm. Both provide excellent sharpness without vignetting. For APS-C a cheap zoom lens may be enough e.g. viewtopic.php?f=27&t=43491
== best, Pawel

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